// ignore_for_file: unnecessary_null_comparison, library_private_types_in_public_api, file_names

import 'package:flutter/material.dart';

class RoundUnderlineTabIndicator extends Decoration {
  /// Create an underline style selected tab indicator.
  ///
  /// The [borderSide] and [insets] arguments must not be null.
  const RoundUnderlineTabIndicator({
    this.borderSide = const BorderSide(width: 2.0, color: Colors.white),
    this.insets = EdgeInsets.zero,
  })  : assert(borderSide != null),
        assert(insets != null);

  /// The color and weight of the horizontal line drawn below the selected tab.
  final BorderSide borderSide;

  /// Locates the selected tab's underline relative to the tab's boundary.
  ///
  /// The [TabBar.indicatorSize] property can be used to define the tab
  /// indicator's bounds in terms of its (centered) tab widget with
  /// [TabBarIndicatorSize.label], or the entire tab with
  /// [TabBarIndicatorSize.tab].
  final EdgeInsetsGeometry insets;

  @override
  Decoration? lerpFrom(Decoration? a, double t) {
    if (a is UnderlineTabIndicator) {
      return UnderlineTabIndicator(
        borderSide: BorderSide.lerp(a.borderSide, borderSide, t),
        insets: EdgeInsetsGeometry.lerp(a.insets, insets, t)!,
      );
    }
    return super.lerpFrom(a, t);
  }

  @override
  Decoration? lerpTo(Decoration? b, double t) {
    if (b is UnderlineTabIndicator) {
      return UnderlineTabIndicator(
        borderSide: BorderSide.lerp(borderSide, b.borderSide, t),
        insets: EdgeInsetsGeometry.lerp(insets, b.insets, t)!,
      );
    }
    return super.lerpTo(b, t);
  }

  @override
  _UnderlinePainter createBoxPainter([VoidCallback? onChanged]) {
    return _UnderlinePainter(this, onChanged);
  }
  // @override
  // BoxPainter createBoxPainter([ VoidCallback? onChanged ]) {
  //   return _UnderlinePainter(this, onChanged);
  // }

  // Rect _indicatorRectFor(Rect rect, TextDirection textDirection) {
  //   assert(rect != null);
  //   assert(textDirection != null);
  //   final Rect indicator = insets.resolve(textDirection).deflateRect(rect);
  //   return Rect.fromLTWH(
  //     indicator.left,
  //     indicator.bottom - borderSide.width,
  //     indicator.width,
  //     borderSide.width,
  //   );
  // }

  // @override
  // Path getClipPath(Rect rect, TextDirection textDirection) {
  //   return Path()..addRect(_indicatorRectFor(rect, textDirection));
  // }
}

class _UnderlinePainter extends BoxPainter {
  // _UnderlinePainter(this.decoration, VoidCallback? onChanged)
  //   : assert(decoration != null),
  //     super(onChanged);

  // final UnderlineTabIndicator decoration;

  _UnderlinePainter(this.decoration, VoidCallback? onChanged)
      : assert(decoration != null),
        super(onChanged);

  final RoundUnderlineTabIndicator decoration;

  BorderSide get borderSide => decoration.borderSide;
  EdgeInsetsGeometry get insets => decoration.insets;

  Rect _indicatorRectFor(Rect rect, TextDirection textDirection) {
    assert(rect != null);
    assert(textDirection != null);
    final Rect indicator = insets.resolve(textDirection).deflateRect(rect);
//    return Rect.fromLTWH(
//      indicator.left,
//      indicator.bottom - borderSide.width,
//      indicator.width,
//      borderSide.width,
//    );
    //希望的宽度
    double wantWidth = 25;
    //取中间坐标
    double cw = (indicator.left + indicator.right) / 2;
    return Rect.fromLTWH(cw - wantWidth / 2,
        indicator.bottom - borderSide.width - 5, wantWidth, borderSide.width);
  }

//   @override
//   void paint(Canvas canvas, Offset offset, ImageConfiguration configuration) {
//     assert(configuration != null);
//     assert(configuration.size != null);
//     final Rect rect = offset & configuration.size;
//     final TextDirection textDirection = configuration.textDirection;
//     final Rect indicator = _indicatorRectFor(rect, textDirection).deflate(borderSide.width / 2.0);
// //    final Paint paint = borderSide.toPaint()..strokeCap = StrokeCap.square;
//     // 改为圆角
//     final Paint paint = borderSide.toPaint()..strokeCap = StrokeCap.round;
//     canvas.drawLine(indicator.bottomLeft, indicator.bottomRight, paint);
//   }

  @override
  void paint(Canvas canvas, Offset offset, ImageConfiguration configuration) {
    assert(configuration != null);
    assert(configuration.size != null);
    final Rect rect = offset & configuration.size!;
    final TextDirection textDirection = configuration.textDirection!;
    final Rect indicator = _indicatorRectFor(rect, textDirection)
        .deflate(decoration.borderSide.width / 2.0);
    final Paint paint = decoration.borderSide.toPaint()
      ..strokeCap = StrokeCap.round;
    canvas.drawLine(indicator.bottomLeft, indicator.bottomRight, paint);
  }
}
